Hydraulic unit for slip-controlled brake systems

ABSTRACT

The present invention relates to a hydraulic unit for slip-controlled brake systems which includes a third row of valves in the accommodating member between a first row of valves having the valve-accommodating bores for the inlet valves and the second housing surface, wherein the third row of valves includes at least in one valve-accommodating bore an electric change-over valve which is closed in its basic position and hydraulically linked to the pump-accommodating bore by way of a portion of a suction channel that traverses the first row of valves for connection to the pump-accommodating bore.

TECHNICAL FIELD

The present invention relates to a hydraulic unit for slip-controlledbrake systems.

BACKGROUND OF THE INVENTION

DE 42 34 013 A1 discloses a hydraulic unit for a slip-controlled brakesystem, including a block-shaped accommodating member which, side byside in a first and second row of valves, comprises a total of eightvalve-accommodating bore accommodating electromagnetically operableinlet and outlet valves. Disposed between the two rows of valves is apump-accommodating bore, and two parallel accumulator-accommodatingbores are arranged outside the rows of valves. Theaccumulator-accommodating bores are arranged transversely to thevalve-accommodating bores directly adjacent to the second row of valvescontaining the outlet valve, while the pump-accommodating bore extendsin parallel to the two rows of valves. Arranged centrally between thetwo rows of valves is a motor-accommodating bore that extends into thepump-accommodating bore paraxially relative to the valve-accommodatingbores.

The disclosed hydraulic unit is appropriate exclusively for a slip-freebraking operation and for being used for brake slip control.

Therefore, an object of the invention is to improve upon a hydraulicunit of the indicated type by simple means in such a fashion that anextension to traction slip control and driving dynamics control ispossible, while the described arrangement of the bores in theaccommodating member accommodating valves, pump and accumulator ismaintained.

According to the invention, a third row of valves is provided openinginto the first housing surface of the accommodating member between thehousing plane provided for the ports of the braking pressure generatorand the housing plane provided for the first row of valves. The thirdrow of valves, which is thus arranged directly adjacent to the first rowof valves, ensures a simple functional extension of the hydraulic unitdesigned for anti-lock control for the purpose of achieving tractionslip control or driving dynamics control, to what end normally closedsolenoid valves configured as electric change-over valves are insertedin the two outside valve-accommodating bores of the third row of valves.Separating valves in the form of solenoid valves open in their basicposition are inserted into the two interposed valve-accommodating boresof the third row of valves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-dimensional illustration of a total view of thesubject matter of the invention for depicting all accommodating boresand pressure fluid channels in the accommodating member.

FIG. 2 is a detail view of FIG. 1 for depicting the channel connectionsbetween the valve-accommodating bores arranged in the third and firstrow of valves and the pump-accommodating bore, as well as the connectionof the accumulator-accommodating bore to the pump andvalve-accommodating bores of the second row of valves.

FIG. 3 is another detail view of FIG. 1 for explaining the channels ofthe first and second row of valves that lead to the wheel and pressuresensor ports.

FIG. 4 is a detail view of FIG. 1 for explaining the pressure fluidreturn existing between the first and second row of valves and theaccumulator-accommodating bores.

FIG. 5 is still another detail view of FIG. 1 with a braking pressuregenerator and separating valve connection modified with respect to FIG.1 and disposed respectively at the valve-accommodating bore receivingthe electric change-over valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a perspective view of a hydraulic unit for slip-controlledbrake systems, including an accommodating member 1 accommodating inletvalves and outlet valves in respectively four valve-accommodating boresX1-X4, Y1-Y4 of a first and second row of valves X, Y that open asblind-end bores into a first housing surface A1 of the accommodatingmember. Housing surface A1 is positioned at right angles relative to asecond housing surface A2 into which several braking pressure generatorand wheel brake ports B1, B2, R1, R3 open. Further, the block-shapedaccommodating member 1 is penetrated by a pump-accommodating bore 5 thatis directed transversely to the direction the valve-accommodating boresX1-X4, Y1-Y4 open into the accommodating member 1. Thepump-accommodating bore 5 is arranged between the axes of thevalve-accommodating bores X1-X4, Y1-Y4 of the first and second row ofvalves X, Y aligned vertically relative to the first housing surface A1.Pointing to the pump-accommodating bore 5 in a vertical distance fromthe first housing surface A1 is a motor-accommodating bore 13 which isnot only used to secure an electric motor that actuates the pump pistonsin the pump-accommodating bore 5 but also comprises a crank drive oreccentric drive.

Two parallel arranged accumulator-accommodating bores 9, which arealigned transversely to the axes of the valve-accommodating bores Y1-Y4of the second row of valves Y, open into the accommodating member 1 in athird housing surface A3 which is disposed parallel opposite the secondhousing surface A2. Spring-applied pistons are inserted into theaccumulator-accommodating bores 9. The depth of theaccumulator-accommodating bores 9 has a smaller size than the horizontaldistance of the second row of valves Y from the third housing surface A3so that the connection between the third row of valves Y and theaccumulator-accommodating bores 9 is established by way of severalreturn channels 10.

Electromagnetically operable, normally closed outlet valves are arrangedin the valve-accommodating bores Y1-Y4 of the second row of valves Y.The vertical axes of the valve-accommodating bores Y1-Y4 of the secondrow of valves Y extend between the two accumulator-accommodating bores 9and the pump-accommodating bore 5 into the accommodating member 1.

To provide a hydraulic connection between a braking pressure generatorport B1 and/or B2 and the wheel brake ports R1, R2 of the first brakecircuit or to the wheel brake ports R3, R4, there is need for severalchannels that connect the valve-, pump- and accumulator-accommodatingbores, that are generally made by appropriate drilling operations withinthe accommodating member 1 exactly as the valve-, accumulator- andpump-accommodating bores.

In order to design the original machining of the accommodating member 1with least possible modifications and hence in a simple fashion, whilebearing in mind the object of the invention, it is suggested that athird row of valves Z be arranged in the accommodating member 1 bestbetween the first row of valves X that includes the valve-accommodatingbores X1-X4 for the inlet valves and the second housing surface A2, saidthird row of valves Z accommodating an electric change-over valve closedin its basic position in a valve-accommodating bore Z1 or Z4 for eachbrake circuit. The hydraulic connection between the valve-accommodatingbore Z1 or Z4 and the pump-accommodating bore 5 is established by way ofa portion of a suction channel 6 traversing the first row of valves Xfor connection to the pump-accommodating bore 5.

Further, at least one valve-accommodating bore Z2 or Z3 is additionallyarranged in the third row of valves Z for each brake circuit, housing anelectromagnetically operable separating valve normally open in its basicposition, with said further valve-accommodating bore Z2 or Z3 beingconnected to the valve-accommodating bore Z1 or Z4 housing thechange-over valve by way of a short channel 3 which is preferablyconfigured as a transverse channel.

Still further, the valve-accommodating bore Z2 or Z3 including theseparating valve is respectively connected to an inlet channel 4 thatleads to the first row of valves X and opens in said first row of valvesX in each case into the bottom of a valve-accommodating bore X2configured as a blind-end bore and receiving an electromagneticallyoperable inlet valve, that is normally open in its basic position. Theinlet channel 4 of each one brake circuit propagates along the first rowof valves X in the direction of a noise damping chamber 7 which opens asa short blind-end bore directly paraxially beside the pump-accommodatingbore 5 into a fourth housing surface A4. On the other hand, thepump-accommodating bore 5 extends through the fourth housing surfaceuntil the opposite housing surface of the accommodating member 1. At theoutside ends of the pump-accommodating bore 5, each one pressure channel8 traverses the pump-accommodating bore 5 in the direction of the noisedamping chambers 7, for what purpose the pressure channel 8 ispreferably designed as a transverse channel that opens radially into theblind-end bore provided for the noise damping chambers 7.

With respect to the details explained so far by way of FIG. 1, referenceis also made to the description in FIG. 2, in as far as the describeddetails do not become apparent from FIG. 1.

The bore portion of the pump which is in each case remote from theoutside ends of the pump-accommodating bore 5 and disposed close to themotor-accommodating bore 13 is penetrated towards eachaccumulator-accommodating bore 9 by the suction channel 6 which opensinto the bottom of the accumulator-accommodating bore 9. Moreover, anon-return valve opening in the direction of the pump-accommodating bore5 is arranged in the short portion of the suction channel 6 positionedbetween the pump-accommodating bore 5 and the accumulator-accommodatingbore 9 so that pressure fluid inflowing from the braking pressuregenerator port B1 or B2 through the electric change-over valve into thefirst portion of the suction channel 6 propagates in each brake circuitexclusively to the suction side of the pump arranged in thepump-accommodating bore 5.

Apart from the short portion of the suction channel 6, at least onereturn channel 10 opens into the bottom of the accumulator-accommodatingbore 9, said channel being connected to the valve-accommodating boresY1, Y2 or Y3, Y4, respectively, receiving the outlet valves and beingarranged in the accommodating member 1 somewhat deeper in relation tothe accumulator-accommodating bore 9. Thus, the second row of valves Yis directly adjacent to the accumulator-accommodating bore 9 so thatshortest possible return channels 10 and short suction channels 9 leadto the accumulator-accommodating bores 9, what improves the evacuation,filling and efficiency of the pump.

In the present example, each valve-accommodating bore Y1, Y2 or Y3, Y4of the second row of valves Y is designed as shortest possible blind-endbore. Each bottom of the valve-accommodating bores Y1-Y2 is respectivelyconnected to a portion of a return channel 10 that leads to theaccumulator-accommodating bore 9. Each return channel 10 is arranged asan angular channel laterally of the short portion of the suction channel6. Downstream of the return channels 10 that open into the bottoms ofthe valve-accommodating bores Y1-Y4, the valve-accommodating bores Y1-Y4are penetrated by the wheel pressure channels 11 which are continuedradially or tangentially by the valve-accommodating bores Y1, Y2 or Y3,Y4, respectively, arranged in the second row of valves (Y) to thevalve-accommodating bores X1, X2 or X3, X4, respectively, arranged inthe first row of valves X. The wheel pressure channels 11 lead past thethird row of valves Z to the wheel brake ports R1, R2 or R3, R4,respectively.

Besides, each one further portion of the wheel pressure channels 11 iscontinued radially or tangentially by the valve-accommodating bores Y1,Y2 or Y3, Y4, respectively, arranged in the second row of valves Ydownstream of the accumulator-accommodating bores 9 to the third housingsurface A3, where one pressure sensor accommodating bore W1-W4 isconnected in each case at the end portion of each one wheel pressurechannel 11 for detecting the brake pressures prevailing at the fourwheel brake ports R1-R4.

FIG. 3 shows in this respect an especially clear illustration of allwheel pressure channels 11 and pressure sensor accommodating bores W1,W2, W3, W4 arranged in the horizontal plane of the first and second rowof valves X, Y.

Finally, the extremely compact arrangement of all channels andaccommodating bores in the accommodating member 1 allows, if necessary,the integration of a blind-end bore for each brake circuit toaccommodate a pump suction damper 12 apart from the valve-accommodatingbore Z1 provided for the change-over valve, to what end the blind-endbore is connected by way of a suction damper channel 2 to thevalve-accommodating bore Z1 accommodating the change-over valve (cf.FIGS. 1 and 5).

Due to the dual-circuit design of the brake circuit, two brakingpressure generator ports B1, B2 and the two wheel brake ports R1, R3open into the second housing surface A2 close to the outside edges ofthe block-shaped accommodating member 4, as becomes apparent fromFIG. 1. As the brake system is meant for a multi-track motor vehiclebeing braked at four wheels, two further wheel brake ports R2, R4 arefitted to the top side of the accommodating member 1, for example.Depending on assembly or mounting conditions, the wheel brake ports R2,R4 may of course also be arranged in the second housing surface A2.

Thus, associated with the first brake circuit is the braking pressuregenerator port B1 which is normally connected to the wheel brake portsR1, R2 by way of the valve-accommodating bores Z1, Z2 in the third rowof valves Z and the valve-accommodating bores X1, X2 in the first row ofvalves X. Hence, in the slip-free braking operation, there is anunimpeded connection through the valve-accommodating bore Z1, thetransverse channel 3, the valve-accommodating bore Z2 and the inletchannel 4 to the open inlet valves in the two valve-accommodating boresX1, X2 of the first row of valves X which are connected directly to thewheel brake ports R1, R2 of the first brake circuit by way of the twowheel pressure channels 11 arranged side by side.

For brake slip control in a pressure reduction phase for the first brakecircuit, there is a pressure fluid connection from the twovalve-accommodating bores X1, X2 through a portion of the wheel pressurechannel 11 to the opened outlet valves in the two valve-accommodatingbores Y1, Y2 so that from there excessive braking pressure volume isconducted through the return channels 10 succeeding the bottoms of thevalve-accommodating bores X1, X2 into the accumulator-accommodating bore9 of the first brake circuit. For the purpose of renewed brakingpressure increase, the pressure fluid of the wheel brakes of the firstbrake circuit stored in said accumulator-accommodating bore is suppliedthrough the short portion of the suction channel 6 from a pump piston inthe pump-accommodating bore 5 to the pressure channel 8, to the noisedamping chamber 7 and again through the portion of the inlet channel 4extending alongside the first row of valves X to the valve-accommodatingbores X1, X2. If the outlet valves in the row of valves Y are closedagain, the pressure fluid delivered by the pump propagates in the caseof pressure increase in the wheel brakes through the opened inlet valvesinto the wheel pressure channels 11 and, thus, to the wheel brake portsR1, R2. If, however, it is desired to keep the wheel brake pressures inone of the wheel brakes constant, then both the inlet valve and outletvalve associated with the wheel brake remain in their closed position,with the result that the connection between the inlet channel 4 and thewheel pressure channel 11 in the first row of valves X and theconnection of the wheel pressure channel 11 to the return channel 10 inthe second row of valves Y are interrupted.

In the brake circuit that has already been described as an example, theseparating valve inserted into the valve-accommodating bore Z2 of thethird row of valves Z is electromagnetically closed and the change-overvalve arranged in the valve-accommodating bore Z1 is opened for tractionslip and driving dynamics control, so that pressure fluid propagatesthrough the braking pressure generator port B1 opening laterally intothe valve-accommodating bore Z1, to the first portion of the suctionchannel 6 arranged at the bottom of the valve-accommodating bore Z1,thus establishing a direct connection to the pump-accommodating bore 5on the shortest way (bypassing the first and second row of valves X, Y).The pump piston inserted into the pump-accommodating bore 5 thensupplies pressure fluid into the pressure channel 8 through the pumppressure valve inserted into the pump-accommodating bore 5 and fromthere through the already mentioned inlet channel 4 to thevalve-accommodating bores X1, X2 which, depending on the prevailingpressure control cycle, are either opened or closed by the inlet valvesin the direction of the wheel brake ports R1, R2.

It can be taken from the three-dimensional illustration of the hydraulicunit of the invention that a pressure fluid channel system is providedbetween the individual rows of valves X, Y, Z by means of straight andtransverse bores, said system permitting an extension to traction slipand driving dynamics control in conformity with the demands ofperformance, while allowing a simplest possible realization in terms ofmanufacture.

Advantageously, the result of the selected position of the third row ofvalves Z for each brake circuit is an especially short, low-resistancesuction channel 6 between the braking pressure generator port B1 or B2and the associated pump-accommodating bore 5. Thus, the suction channel6 is quick and ready to vent and fill. In addition, a piston pump in thepump-accommodating bore 5 is used to aspirate the pressure fluid quicklyand reliably on the shortest way through the braking pressure generatorport B1 or B2.

The statements made so far with respect to the first brake circuit applyaccordingly with respect to the design and the function of the elementsnecessary for the second brake circuit, which are arrangedmirror-symmetrically to the elements of the first brake circuit in theaccommodating member 1.

To illustrate the previously described construction and function of thehydraulic unit, the arrangement of bores in the block will be describedin the following by way of FIGS. 2 to 5 for the parts of theaccommodating member 1 partly concealed in FIG. 1.

To this end, FIG. 2 shows a detail view of FIG. 1 for explaining theconnections between the valve-accommodating bores Z2, Z3 arranged in thethird and first row of valves Z, X and the pump-accommodating bore 5through the inlet channel 4 for each brake circuit. Thereby, thepressure fluid supplied by the pump propagates either through the inletvalves switched open in the first row of valves X to the wheel pressurechannels 11 and, hence, to the wheel brake ports R1, R2 (see FIG. 3) orretroacts in the closed position of the inlet valves to the separatingvalve in the valve-accommodating bore Z2 by way of the inlet channel 4connecting the first row of valves X and the third row of valves Z.Thus, in the normally opened switch position of the separating valve,the pump pressure in the previously explained closing position of theinlet valve retroacts through the channel 3 that is laterally connectedto the valve-accommodating bore Z3 into the valve-accommodating bore Z1and to the braking pressure generator port B1 (see also FIG. 1).

It becomes apparent from FIG. 2 that the portion of the inlet channel 4that extends transversely to the third and the first row of valves Z, X,in terms of manufacture, is made as a blind-end bore using the secondhousing surface A2 by means of a simple drilling operation upstream ofthe valve-accommodating bores Z2, X2. The actual connection of thechannel portion extending transversely to the rows of valves X, Z isthen constituted by respectively one drilling operation pointing fromthe first housing surface A1 to the valve-accommodating bores Z2, X2,said drilling operation penetrating the bottoms of thevalve-accommodating bores Z2, X2 in the direction of the channel portionof the inlet channel 4 placed on top thereof and cutting the channelportion.

Likewise, the portion of the inlet channel 4 that extends horizontallyabove alongside the first row of valves X is provided from the fourthhousing surface A4 by means of a drilling operation cutting the inletchannel 4. The connection between the outside valve-accommodating boreX1 and the horizontal portion of the inlet channel 4 is then constitutedby a drilling operation directed from the first housing surface A1vertically through the valve-accommodating bore X1, unless a directintersection of the bottoms of the valve-accommodating bores X1, X2 isprovided already during the horizontal drilling operation for making theinlet channel 4.

In the present example, the horizontal portion of the inlet channel 4opens into a noise damping chamber 7 arranged in the area of the fourthhousing surface A4 and connected to the pressure side of thepump-accommodating bore 5 by way of a pressure channel 8. Said pressurechannel 8 is provided by means of a bore that is directed transverselyfrom above into the accommodating member 1 and penetrates the outsideend area of the pump-accommodating bore 5 until the intersection of thenoise damping chamber 7. Both the noise damping chamber 7 and thetransverse port of the pressure channel 8 are closed pressure-tightly tothe outside by means of plugs.

FIG. 3 shows a cutout of the accommodating member 1 in the area of theportions of the wheel pressure channels 11 connecting the first andsecond row of valves X, Y to the wheel ports R1-R4 and the pressuresensor accommodating bores W1-W4. According to the illustration, thefour wheel pressure channels 11 necessary for the wheel brakes pointparallel side by side from the third housing surface A3 to the parallelarranged valve-accommodating bores X1-X4, Y1-Y4. The necessary drillingtool fully penetrates to this end the valve-accommodating bores of thesecond row of valves Y and cuts the walls of the valve-accommodatingbores in the first valve-accommodating bore X. The link between thewheel brake ports R1-R4 and the valve-accommodating bores in the firstrow of valves X is established by way of the end portion of the wheelpressure channels 11 depending on the position of the wheel brake portsR1-R4. Depending on the position of the wheel brake ports R1-R4 chosen,a transverse or cross bore may be suitable to this end. The ends of thewheel pressure channels 11 are sealingly closed in the third housingsurface A3, while the pressure sensor accommodating bores W1-W4 arrangedparallel directly beside the second row of valves Y in a fourth track ofpunched holes W are closed by means of suitable sensors which exactly asthe valves in the rows of valves normally project from the first housingsurface A1.

Following FIG. 3, FIG. 4 shows the connection of eachvalve-accommodating bore of the second row of valves Y through thereturn channels 10 to the accumulator-accommodating bores 9 disposedabove the track of punched holes W. Each return channel 10 is continuedas an angular channel produced by the conjunction of a horizontal and avertical drilling operation, for what purpose one drilling operation isdirected into the respective valve-accommodating bore of the second rowof valves Y and into the bottom of the accumulator-accommodating bore.Further, all vertical ports of the inlet channels 4 at the bottoms ofthe four valve-accommodating bores X1-X4 in the first row of valves Xand the wheel pressure channels 11 opening at the periphery of thevalve-accommodating bores X1-X4 are apparent.

FIG. 5 finally shows another detail view of the subject matter of theinvention with a braking pressure generator and separating valveconnection, modified compared to FIG. 1, at the valve-accommodating boreZ1 receiving the electric change-over valve. The channel of the brakingpressure generator port B1 or B2 now opens in an elevated position intothe second housing surface A2 so that said is continued above the bottomof the valve-accommodating bore Z1 linearly to the accommodating bore ofthe pump suction damper 12. Consequently, the first portion of thesuction channel 6 will now succeed below the bottom at the wall of thevalve-accommodating bore Z1. The exchange of the channel ports now madecompared to FIG. 1 allows reverse fluid flow through thevalve-accommodating bore Z1 and, thus, also the change-over valve incase of need.

Further, the channel 3 in FIG. 5 is led as a transverse channel directlyfrom the first housing surface A1 through the valve-accommodating boreZ2 to the point of connection of the braking pressure generator port B1or B2 to the bottom of the valve-accommodating bore Z1. Further, anotherpressure sensor port 14 is arranged between the twoaccumulator-accommodating bores in FIG. 5, said port 14 being connectedto the accommodating bore of the pump suction damper 12 by way of apressure measuring channel traversing the pump-accommodating bore 5,with the result that the pressure prevailing at the braking pressuregenerator port B2 can be detected by means of an appropriate sensorsystem.

As far as further details illustrated in FIG. 5 are concerned, referenceis made to the preceding explanations given with respect to FIGS. 1-4.

1-12. (canceled)
 13. Hydraulic unit for slip-controlled brake systems,comprising: an accommodating member accommodating inlet and outletvalves in several valve-accommodating bores of a first and second row ofvalves that open into a first housing surface of the accommodatingmember which is positioned at an angle relative to a second housingsurface, opening into whose area are preferably several braking pressuregenerator ports and/or wheel brake ports, a pump-accommodating borearranged in the accommodating member and aligned transversely to thedirection the valve-accommodating bores open into the accommodatingmember, wherein the pump-accommodating bore is arranged between the axesof the valve-accommodating bores of the first and second row of valves,a motor-accommodating bore arranged in the accommodating member andpointing to the pump-accommodating bore, an accumulator-accommodatingbore opening into the accommodating member transversely to the axes ofthe valve-accommodating bores in a third housing surface that isopposite to the second housing surface, outlet valves arranged in thevalve-accommodating bores of the second row of valves, wherein in thesecond row of valves the axes of the valve-accommodating bores betweenthe accumulator-accommodating bore and the pump-accommodating bore pointinto the accommodating member, and including several channelsinterconnecting the valve-, pump- and accumulator-accommodating boresand being able to provide a hydraulic connection between a brakingpressure generator and several wheel brakes, wherein a third row ofvalves is arranged in the accommodating member between the first row ofvalves including the valve-accommodating bores for the inlet valves andthe second housing surface, with the third row of valves including atleast in one valve-accommodating bore an electric change-over valvewhich is closed in its basic position and hydraulically linked to thepump-accommodating bore by way of a portion of a suction channel thattraverses the first row of valves for connection to thepump-accommodating bore.
 14. Hydraulic unit as claimed in claim 13,wherein at least one further valve-accommodating bore of the third rowof valves, into which a separating valve is inserted, is connected tothe valve-accommodating bore containing the change-over valve by way ofa channel, preferably a transverse channel.
 15. Hydraulic unit asclaimed in claim 14, wherein the valve-accommodating bore containing theseparating valve is connected to an inlet channel that leads to thefirst row of valves and opens in the first row of valves into the bottomof a valve-accommodating bore which is designed as a blind-end bore andreceives an inlet valve.
 16. Hydraulic unit as claimed in claim 15,wherein the inlet channel is continued along the first row of valves inthe direction of a noise damping chamber that opens directly adjacent tothe pump-accommodating bore into a fourth housing surface into whichalso the pump-accommodating bore extends.
 17. Hydraulic unit as claimedin claim 16, wherein a pressure channel extends radially through thepump-accommodating bore at the outside end of the pump-accommodatingbore in the direction of the noise damping chamber, for what purpose thepressure channel is designed preferably as a transverse channel whichopens radially into a blind-end bore provided for the noise dampingchamber.
 18. Hydraulic unit as claimed in claim 13, wherein thepump-accommodating bore is penetrated by the suction channel in thedirection of the accumulator-accommodating bore, with the suctionchannel opening into the bottom of the accumulator-accommodating bore.19. Hydraulic unit as claimed in claim 18, wherein a non-return valveopening in the direction of the pump-accommodating bore is inserted intothe portion of the suction channel which is positioned between thepump-accommodating bore and the accumulator-accommodating bore. 20.Hydraulic unit as claimed in claim 18, wherein a return channel opensinto the bottom of the accumulator-accommodating bore, said channelbeing connected at least to one of the valve-accommodating boresaccommodating the outlet valves and arranged directly adjacent to theaccumulator-accommodating bore in the second row of valves. 21.Hydraulic unit as claimed in claim 20, wherein each valve-accommodatingbore of the second row of valves is configured as a blind-end bore, atthe bottom of which a return channel leading to theaccumulator-accommodating bore is connected.
 22. Hydraulic unit asclaimed in claim 21, wherein the return channel extends past thepump-accommodating bore in each case radially or tangentially throughthe valve-accommodating bore arranged in the second row of valves to thevalve-accommodating bore, which is arranged in the first row of valvesand connected to the wheel brake port arranged beside and above thethird row of valves by means of a wheel pressure channel led past thethird row of valves.
 23. Hydraulic unit as claimed in claim 22, whereina portion of the return channel extends radially or tangentially throughthe valve-accommodating bore arranged in the second row of valves, pastthe accumulator-accommodating bore to the third housing surface, and apressure sensor accommodating bore is connected to this portion of thereturn channel.
 24. Hydraulic unit as claimed in claim 13, whereinadjacent to the valve-accommodating bore provided for the change-overvalve, a blind-end bore is provided in the accommodating member toaccommodate a pump suction damper, said blind-end bore being connectedby way of a pressure channel to the valve-accommodating bore receivingthe change-over valve.